In recent times, there has been a rapid increase in use of technologies such as virtual reality, augmented reality, and so forth, for presenting a simulated environment (or a virtual world) to a user. Typically, the user uses a device (for example, such as a virtual reality device, an augmented reality device, and the like) for experiencing such a simulated environment. Furthermore, in use, the user generally wears (namely, supports) the device on his/her head.
Nowadays, such devices often employ a technique such as gaze-tracking (namely, eye tracking) to determine a gaze direction of the user. Typically, the gaze-tracking is associated with determination of position of pupils of eyes of the user. Generally, an illumination source is employed for emitting light towards the user's eyes, and a camera is employed for capturing an image depicting the pupils of the user's eyes and reflection(s) of the emitted light from the user's eyes. In such an instance, the captured image is employed to determine the gaze direction of the user.
Examples of commonly used gaze-tracking techniques employed in the aforesaid devices include a bright-pupil tracking technique and a dark-pupil tracking technique. In the bright-pupil tracking technique, the illumination source and the camera are positioned coaxially with the gaze direction of the user's eye. In such an instance, the emitted light is substantially reflected from a retina of the user's eye towards the camera, thereby producing a bright pupil effect in the captured image of the user's eye. On the other hand, in the dark-pupil tracking technique, the illumination source and the camera are positioned at an angle that is offset from the gaze direction of the user. In such an instance, the emitted light is reflected away from the camera, thereby producing a dark pupil effect in the captured image of the user's eye.
However, there exist a number of limitations associated with implementations of the aforementioned gaze-tracking techniques. Firstly, the illumination source and the camera are required to have specific positions with respect to the user's eyes for accurate gaze tracking. Typically, in devices employing the dark-pupil tracking technique, the illumination source and/or the camera may be positioned near a periphery of the user's eyes, and consequently, may be substantially obstructed by the user's eyelids, eye lashes and so forth. Such obstructions reduce an accuracy of the gaze-tracking. Secondly, in some conventional techniques, a hot mirror is required to be arranged within the device to align the camera along a central gaze direction of the user. Such devices are made large in size so as to accommodate the hot mirror, and are prone to suboptimal gaze-tracking when the user's gaze direction is positioned away from the center of the user's eyes. Thirdly, existing gaze-tracking techniques do not compensate for changes in pupil shape as per an apparent shape of the user's eyes from different directions. Consequently, additional inaccuracies (for example, such as geometric aberrations, reflection artefacts, and the like) are introduced in the gaze-tracking.
Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks associated with conventional gaze-tracking techniques.